This invention relates to loose-leaf binders and, more particularly, to a vinyl loose-leaf binder cover having an improved hinge and the process for making the same.
Loose-leaf binders, also sometimes referred to as notebooks, are commonly used in schools, homes and businesses to store loose-leaf paper. Loose-leaf binders usually consist of a vinyl cover portion and a metal ring or clasp portion. Paper is retained by the rings or clasp within the cover.
The binder cover usually consists of front, back and side portions composed of sheets of vinyl stiffened by cardboard inserts. Usually, the juncture of the side with the front and back portions are hinges integrally formed out of the vinyl sheets. The vinyl sheets are welded between the cardboard inserts so that the hinge area is more narrow than the portions of the cover on either side of the hinge, thereby permitting the front and back to be folded relative to the side and rotated relative to the hinge.
Welding the vinyl causes components of the vinyl, notably plasticizer, to be removed. The reduction in thickness and in the amount of vinyl and plasticizer resulting during the welding process weakens the hinge area and tends to contribute to an eventual splitting or tearing of the vinyl resulting from normal use along the hinge, and particularly along the vertical boundary of the hinge with the side, front and back portions of the cover. This problem has been found to be compounded by the shape of the welding die used to create the hinge. Most commonly, the die is a flat strip of brass having a flat, squared-off welding surface. This shape of die creates a correspondingly flat, squared-off shaped hinge in the vinyl. The boundaries of the hinges with the other portions of the cover are vertical lines running from the top to the bottom of the binder cover, and that is where splitting generally occurs.
To combat this problem, some binder covers have hinges which are welded with lightly etched welding dies. The die is impressed into the vinyl to the full length of the etchings, and sometimes beyond, which creates a hinge having alternating horizontal ridges and indentations. While this type of die removes less vinyl from the hinge area than does the squared-off die, it still produces substantially continuous vertical boundaries with the adjacent portions of the cover, and splitting occurs frequently.
Accordingly, an object of this invention is to provide a loose-leaf binder cover having a new and improved hinge and a process for making the same. A more particular object is to provide a hinge for a loose-leaf binder cover which is stronger and more resistant to splitting and tearing.
In keeping with one aspect of the invention, a hinged loose leaf binder cover is constructed from three flat rigid inserts placed between a pair of sheets of thermoplastic material. The edges of these sheets are melted to seal them. An embossed die is applied along a length of the sheets between the inserts to a depth less than the full height of the embossment so that the longitudinal edges of the embossed surface of the die do not contact the sheets. The sheets are then allowed to cool and harden.
The above-mentioned and other features of this invention and the manner of obtaining them will become more apparent, and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings.